In a conventional vehicle or work machine, an engine controller communicates with a transmission controller and other controllers over a communication link such as a Society of Automotive Engineers (SAE) J-1939 communications protocol. Communication may include information such as torque, speed, power, and the like. The communication over the link allows the controllers to optimally control the engine, transmission and any other device.
When a communication loss or interruption occurs, however, the controllers are unable to communication with one another. This can be problematic particularly if operating at a high torque or speed level, and an operator desires to change the operation of the vehicle or machine, e.g., shift into a different range. To protect the transmission and its internal components, the transmission controller may communicate certain torque level requirements to the engine controller to maintain engine torque at a certain level, for example. When the communication between controllers is either lost or intermittently interrupted, the controllers may not be able to communicate with one another. As a result, high or varying output torque from the engine can present problems to the transmission.
Thus, there is a need for a method and system to protect the transmission in the event of a loss of communication, whether intermittently or for a longer duration.